1. Field of the Invention
The present invention relates to a bandgap reference (BGR) circuit and more particularly to a BGR circuit for generating a reference voltage by using a MOS (Metal Oxide Semiconductor) transistor.
2. Description of the Background Art
Today, an analog circuit using a MOS transistor is replacing a conventional analog circuit using a bipolar transistor. Many of recent ICs (Integrated Circuits) have already been implemented by a CMOS process. A BGR circuit is a reference voltage generating circuit using a bandgap voltage and extensively used for measurement and control purposes. A BGR is capable of generating an extremely stable, low reference voltage.
However, conventional BGR circuits has some problems that will be described specifically later. Particularly, the conventional BGR circuit cannot reduce an error with respect to a designed reference voltage or a temperature drift.
Technologies relating to the present invention are disclosed in, e.g., Japanese Patent Laid-Open Publication Nos. 6-175743, 10-232724, 11-161355, 2000-75945 and 2000-181554.
It is an object of the present invention to provide a BGR circuit capable of reducing an error with respect to a designed reference voltage and a temperature drift.
A BGR circuit of the present invention includes a first serial circuit made up of a first diode, a first transistor, and a first resistor. A second serial circuit includes a second diode having a greater current feed area than the first diode, a second transistor, and a second resistor. An amplifier amplifies a difference between the voltage drop of the first resistor and that of the second resistor. A third serial circuit includes a third transistor control led by the output of the amplifier, a third resistor and a fourth resistor, and a third diode. Opposite ends of the fourth resistor are respectively connected to the gate of the first transistor and the gate of the second transistor. A reference voltage appears on opposite ends of the portion of the third serial circuit including the third resistor, fourth resistor, and third diode.